Drip-absorbing sheet

ABSTRACT

A drip-absorbing sheet comprising a powdery or granular edible saccharide supported and laminated between a semipermeable membrane and a water-absorbing porous sheet. This drip-absorbing sheet has a simple structure and can be automatically manufactured without the need for a large labor force, thus reducing the manufacturing cost. This sheet can be cut to an optional size according to an intended use, and the incorporated saccharide will not drop from the cut portion.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a low-cost drip-absorbing sheet forabsorbing and separating drips generated from perishable foods, toprevent a lowering of the quality of the foods.

(2) Description of the Related Art

In perishable foods such as meat, fish, vegetables and fruits(hereinafter referred to as "foods"), when the cells thereof aredestroyed, fluids inside and outside the cells flow out, resulting in aloss of freshness of the foods.

This loss of freshness causes a lowering of the water retention of foodsand an increased quantity of an exudate, i.e., "drip", whereupon anautolysis of the foods, a propagation of bacteria, an oxidation oflipids, and a discoloration of the foods occur, and the lowering of thequality thereof is accelerated.

It is well-known in the food industry that, if the drips thus generatedcan be separated, this will effectively maintain the freshness of foods.Nevertheless if foods are stored in the state where drips generated fromfoods are absorbed in paper, sponge or the like, although it seems thatthe drips are separated from the foods, the foods are always in contactwith the drips and the effect of maintaining the freshness thereofcannot be obtained.

On the other hand, if a part of water contained in foods is separated inadvance, and the foods are stored in this state, the generation of dripsis controlled and the freshness effectively maintained.

Also the method of storing foods while absorbing and separating dripsexuding from the foods is effective.

As the food-preserving method, there has been long adopted a method inwhich foods are placed in direct contact with a water-absorbingsubstance, to remove water from the foods and improve the preservabilitythereof, but this method is defective in that the taste of the foods ischanged.

With the development of water-absorbing polymers, as the means forreducing the water content in foods or removing generated drips withoutchanging the taste of the foods, there have recently been proposedvarious water-removing sheets comprising a combination of awater-absorbing polymer and a semipermeable membrane (see, for example,Japanese Examined Utility Model Publication No. 58-43922, JapaneseExamined Patent Publication No. 58-58124, Japanese Examined UtilityModel Publication No. 61-3337, Japanese Examined Patent Publication No.1-22816 and U.S. Pat. No. 4,383,376), and water-removing sheetscomprising a semipermeable membrane and a liquid saccharide (see U.S.Pat. No. 4,819,342). These sheets are utilized for removing water fromfoods in advance, before storage, or for separating drips generated fromfoods during storage.

In these water-removing sheets, a granular polymeric water absorber or aliquid saccharide is used and enveloped so that one surface of theenvelope is formed of a semipermeable membrane, and the periphery of thesemipermeable membrane is bonded to effect a sealing thereof.Accordingly, the water-absorbing sheet of this type is advantageous inthat the sheet can be used repeatedly, but a special technique orapparatus is necessary for the production and the number of steps ishigh and therefore, the manufacturing cost is increased.

Furthermore, since the sheet is marketed in the state where theperiphery is bonded and sealed, variations of the sizes are limited anda user must select an appropriate size: often it is impossible to obtaina sheet having a desirable size.

SUMMARY OF THE INVENTION

The inventors carried out research with a view to solving the foregoingproblems, and considered that, if a drip-absorbing sheet is prepared byusing a material that will not give problems concerning food sanitation,without bonding and sealing the periphery of a semipermeable membrane, asheet having a desirable size can be optionally obtained by cutting, thenumber of manufacturing steps can be reduced, and a product having a lowprice can be provided.

The present invention has been completed based on the aboveconsideration, and a primary object of the present invention is toprovide a low-cost throwaway drip-absorbing sheet that can be used afterbeing cut to a required size.

In accordance with the present invention, this object can be attained bya drip-absorbing sheet comprising a powdery or granular ediblesaccharide supported and laminated between a water-permeablesemipermeable membrane and a water-absorbing porous sheet.

In the present invention, preferably the amount of the powdery orgranular edible saccharide is from 10 to 200 g/m², and the weight of thewater-absorbing porous sheet is 0.2 to 10 times the weight of the ediblesaccharide.

In view of the handling ease, preferably the sheet is partially bondedthrough an adhesive, as long as the water permeability is not adverselyaffected.

Moreover, in the present invention, the semipermeable membrane and thewater-absorbing porous sheet can be bonded by using an edible saccharidehaving a melting point lower than the melting temperature orcarbonization temperature of the semipermeable membrane orwater-absorbing porous sheet, and heat-pressing the laminate.

Since the drip-absorbing sheet of the present invention has theabove-mentioned structure, even if the sheet is used after cutting to arequired size, no problems arise concerning food sanitation, and dripsremoved through the semipermeable membrane can be separated from foods.Moreover, the structure is simple and the sheet can be automaticallymanufactured by an apparatus without the need for a large labor force.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinally sectional view illustrating one embodiment ofthe drip-absorbing sheet of the present invention; and,

FIG. 2 is a diagram illustrating an example of the state of use of thesheet shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows an embodiment of the drip-absorbing sheet (hereinafterreferred to as "absorbing sheet") 1 according to the present invention.In FIG. 1, reference numeral 2 represents a water-permeablesemipermeable membrane which is arranged as the front surface material,and a water-absorbing porous sheet 3 (hereinafter referred to as "poroussheet") is arranged as the back surface material. A powdery or granularsaccharide 4 is supported between the semipermeable membrane 2 andporous sheet 3. If the semipermeable sheet 2 and porous sheet 3 arebonded at points appropriately spaced from one another by using anadhesive 5 within a range not affecting the water permeability, a mutualdivergence does not occur between the semipermeable membrane 2 andporous sheet 3, and the sheet can be handled very easily.

When a perishable food 6 is placed on the semipermeable membrane 2 ofthe absorbing sheet 1 having the structure as shown in FIG. 2, a part ofwater contained in the food permeates through the semipermeable membrane2 while swelling the permeable membrane 2. The saccharide 4 is dissolvedby this permeating water to form an aqueous solution and generate astrong osmotic pressure, with the result that a water-absorbing functionis exerted. This water-absorbing force is maintained until thedifference of the osmotic pressure between the food 6 and the aqueoussolution of the saccharide disappears. The aqueous solution of thesaccharide formed by this absorption of water is absorbed and retainedin the porous sheet 3, and accordingly, the drip is completely separatedfrom the food by the semipermeable membrane 2 and the freshness of thefood is maintained.

Each of the semipermeable membrane 2, porous sheet 3, and saccharide 4used for the absorbing sheet 1 of the present invention must be composedof a material which is safe even when in direct contact with food.

As the semipermeable membrane 2, there can be mentioned, for example, ausual cellophane sheet and a completely saponified polyvinyl alcoholsheet.

As the saccharide, there can be used low-molecular-weight solidsaccharides such as fructose, glucose, oligosaccharide, maltose, powdercorn syrup and sucrose. These saccharides have a low permeabilitythrough a semipermeable membrane and have a high osmotic pressure, andthus show a strong water-absorbing property.

Further, these saccharides can be used in the form of mixtures of two ormore thereof. Furthermore, these saccharides can be mixed with otherwater-soluble polymeric compound such as sodium slginate, carboxy-methylcellulose or starch, whereby the viscosity of the aqueous solution ofthe saccharide is increased the force of retaining the aqueous solutionof the saccharide in the porous sheet 3 can be increased and thewater-absorbing capacity can be increased.

As the porous sheet, there can be mentioned, for example, a paper sheet,a fabric, a nonwoven fabric and a foamed sponge, but any materials thatcan absorb water therein and are safe even when in contact with foods,in the form of a sheet, can be used without particular limitation.

A starch type adhesive is most preferably used as the adhesive from theviewpoint of food sanitation, but other materials that can be used as afood-packaging material can be used in the present invention.

The materials admitted as materials for foods, such as foods per se,food additives and food-packaging materials, must be used as theconstituent materials of the absorbing sheet of the present invention.

The absorbing sheet of the present invention is prepared by uniformlyscattering the powdery or granular edible saccharide on the porous sheet3, piling the semipermeable member having an adhesive coated on thesurface thereof in the form of dots having a diameter of 100 to 500 μmat a density of 10 to 100 dots per cm², and pressing the assembly topartially bond and integrate the porous sheet 3 and the semipermeablemembrane. The amount of the saccharide scattered on the porous sheet 3per m² of the sheet is small, and thus the bonding is not hindered bythe saccharide.

The above operation is carried out continuously by using an appropriateapparatus, and the formed sheet is wound in the form of a roll or is cutto prepare a long absorbing sheet 1.

The sheet is used after it is cut to a required size according to theintended use. At this step, the powdery or granular saccharide coulddrop from the cut portion, but by sucking the cut portion, this can beprevented to an extent such that no practical problem arises.

If a saccharide having a melting point lower than the meltingtemperature or carbonization temperature of the semipermeable membraneor water-absorbing porous sheet is used as the edible saccharide, andthe assembly is heat-pressed from both the surfaces at a temperaturelower than the melting temperature or carbonization temperature to meltthe saccharide, the semipermeable membrane and water-absorbing poroussheet are bonded through the saccharide and a drip-absorbing sheet isformed.

In this absorbing sheet, selection of the semipermeable membrane,water-absorbing porous sheet and edible saccharide to be combined islimited, but even if the absorbing sheet is freely cut, a dropping ofthe saccharide from the cut portion does not occur and the absorbingsheet can be easily prepared.

The amount scattered of the saccharide is determined according to theamount of drips generated from the food to be dehydrated. In the case offish and meat, the amount of drips is about 3% based on the weight ofthe food, and the saccharide is preferably scattered in an amount ofabout 20 g/m². In the case of a frozen food, the amount of drips islarge, in an extreme case the amount of drips is as large as 20% basedon the weight of the food. Accordingly, in this case, the saccharidemust be scattered in an amount of about 150 g/m².

If the amount scattered of the saccharide is too small, a dehydratingeffect cannot be attained, and if the amount scattered of the saccharideis too large, bonding between the semipermeable membrane and the poroussheet becomes difficult, i.e., the effect is not improved over a certainlevel and the sheet becomes disadvantageous in view of the cost.Therefore, the amount scattered of the saccharide is appropriatelyselected within the range of from 10 to 200 g/m², according to the kindof the food to be dehydrated.

The base weight of the porous sheet per unit area is preferably adjustedto 20 to 200 g/m², in view of the retention amount of the saccharide andthe water absorption quantity. When the amount of drips generated fromthe objective food is large, the base weight of the porous sheet must beincreased, but since the above-mentioned porous sheet can absorb andretain the aqueous solution of the saccharide in an amount (weight)about 20 times the weight of the porous sheet under atmosphericpressure, preferably a porous sheet having a base weight about 0.2 to 10times the weight of the saccharide is used.

The present invention will now be described in detail with reference tothe following examples, that by no means limit the scope of theinvention.

EXAMPLE 1

Various foods were brought into contact with a conventionalwater-removing sheet having a large water-absorbing capacity (Pichit®Sheet supplied by Showa Denko), placed in a refrigerator at 3° to 5° C.,and the flow-out rates of the drips were measured.

The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    Food                   Contact Bottom                                                                        Contact                                                                             Amount Generated                                                                        Drip Flow-Out Rate             Run No.                                                                            Kind     Amount Used                                                                            Area (dm.sup.2)                                                                       Time (hr)                                                                           of Drips (g)                                                                            (g/dm.sup.2 ·         __________________________________________________________________________                                                   hr)                            1    Slice of cod                                                                            80 g/slice × 20                                                                 11.25   8     80        0.89                           2    thawed cleft tuna                                                                      200 g    1.6     5     12        1.5                            3    tuna (raw)                                                                             200 g    1.6     12    5         0.26                           4    red fish pickled                                                                       300 g/slice × 2                                                                  2.7     8     24        1.11                                in sake lees                                                             5    raw chicken                                                                            250 g    1.5     8     15        1.25                                ham meat                                                                      without skin                                                             6    cut fruit                                                                              150 g    0.64    4     6.0       2.3                            __________________________________________________________________________

From the results shown in Table 1, the drip flow-out rates of the foodsare in the range of from 0.2 to 3.0 g/dm².hr, and water-removing sheetsmust have a water-absorbing capacity exceeding such drip flow-out rates.

EXAMPLE 2

Drip-absorbing sheets were prepared by using natural material asmentioned below.

A cellophane paper (PT300 supplied by Tokyo Cellophane) was used as thesemipermeable membrane.

Anhydrous crystalline fructose (AHC Arc supplied as Sanmatsu Kogyo) andrefined white sugar (supplied by Mitsui Seito) were used as thesaccharide.

A paper towel (supplied by Daio Seishi) was used as the water-absorbingporous sheet.

A starch paste was used as the adhesive.

Sheets were prepared by scattering various amounts of the saccharide onpaper towels differing in thickness, piling the cellophane paper havingthe starch paste coated in the form of dots on the surface thereof, andpress-bonding the assemblies. The amount used of the saccharide and thebase weight of the paper towel are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                        Amount Used of  Base Weight of                                Sheet Fructose  Refined White Sugar                                                                           Paper Towel                                   No.   (g/m.sup.2)                                                                             (g/m.sup.2)     (g/m.sup.2)                                   ______________________________________                                        1     200       --              120                                           2     100       --              80                                            3      20       --              40                                            4      10       --              80                                            5     --        150             80                                            6     --         50             40                                            7     cellophane was dot-bonded to                                                                        40                                                      paper towel without using                                                     saccharide                                                              ______________________________________                                    

The above sheets were brought into contact with bean curd (having athickness of 2.2 cm and a contact area of 0.9 dm²), opened and driedhorse mackerel (having a contact area of 1 dm²), and sliced radish(having a thickness of 1.7 cm and a contact area of 1 dm²) at roomtemperature (20° C.) for 3 hours, and the drip-absorbing rates weredetermined. The results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Food                                                                                               Opened and                                                                    Dried Horse                                              Sheet   Bean Curd    Mackerel   Sliced Radish                                 No.     (g/dm.sup.2 · hr)                                                                 (g/dm.sup.2 · hr)                                                               (g/dm.sup.2 · hr)                    ______________________________________                                        1       5.9          1.8        2.8                                           2       5.7          1.7        2.8                                           3       5.6          1.2        0.8                                           4       4.3          0.3        0.4                                           5       5.5          1.8        2.6                                           6       5.5          1.3        0.7                                           7       1.8          0.1        0.2                                           ______________________________________                                    

EXAMPLE 3

Drip-absorbing sheets were prepared by using the synthetic materialsdescribed below.

A polyvinyl alcohol film (LH-18 supplied by Tokyo Cellophane) was usedas the semipermeable membrane, powdery malt (SLD-25 supplied by SanmatsuKogyo) was used as the saccharide, foamed urethane sponge was used asthe water-absorbing sheet, and a commercially available adhesive(Takelac A-712-B/Takenate A-72B supplied by Takeda Yakuhin Kogyo) wasused as the adhesive.

Drip-absorbing sheets were prepared in the same manner as described inExample 2, by using the foregoing materials. The amount of the powderymalt and the base weight of the foamed urethane sponge are shown inTable 4.

                  TABLE 4                                                         ______________________________________                                                                 Base Weight of Foamed                                Sheet Powdery Malt       Urethane Sponge                                      No.   (g/m.sup.2)        (g/m.sup.2)                                          ______________________________________                                         8     40                40                                                    9     80                40                                                   10    120                40                                                   11    polyvinyl alcohol sheet was                                                                      40                                                         dot-bonded to foamed urethane                                                 sponge without using powdery                                                  malt                                                                    ______________________________________                                    

The foregoing sheets were placed in contact with devil's-tongue paste(having a thickness of 3.7 cm and a contact area of 1.2 dm²) and rawtuna (having a thickness of 1.4 cm and a contact area of 1.6 dm²) in arefrigerator at 2° C. for 8 hours, and the drip -absorbing rates weremeasured. The results are showing Table 5.

                  TABLE 5                                                         ______________________________________                                                 Food                                                                 Sheet      Devil's-tongue Paste                                                                        Raw Tuna                                             No.        (g/dm.sup.2 · hr)                                                                  (g/dm.sup.2 · hr)                           ______________________________________                                         8         1.13          0.40                                                  9         1.86          0.63                                                 10         2.08          0.81                                                 11         0.23          0.12                                                 ______________________________________                                    

EXAMPLE 4

Anhydrous crystalline fructose (supplied by Sanmatsu Kogyo and having amelting point of 146° C.) was scattered in an amount of 100 g/m² andsupported between a cellophane paper (RT-300 supplied by TokyoCellophane) and a paper towel (supplied by Daio Seishi). The assemblywas heat-pressed at a temperature of 160° C. under a pressure of 30kg/cm² for 20 seconds, by using a hot press to melt the fructose andbond the cellophane tape to the paper towel, whereby a paper-absorbingsheet was prepared. When this sheet was cut, dropping of the saccharidefrom the cut portion did not occur. The water-absorbing capacity of thiswater-absorbing sheet was equivalent to that of water-absorbing sheetNo. 2 of Example 2.

The following can be seen from the results obtained in Examples 1through 4.

(a) If a saccharide is not present, the water-absorbing property is lowand the sheet cannot be practically used.

(b) Even if the amount of the saccharide exceeds 200 g/m², no furtherimprovement of the performance is attained and the use of such a largeamount of the saccharide has no significance.

(c) The water-absorbing capacity of fructose is higher than that ofsucrose, and as the molecular weight is low, the water-absorbingcapacity is high.

(d) The aqueous solution of the saccharide formed by an absorption ofwater can be sufficiently retained if the water-absorbing porous sheetis used in an amount (weight) 0.2 to 10 times the weight of thesaccharide.

(e) A variety of drip-absorbing sheets having high performances can beprepared by using the combination of semipermeablemembrane/saccharide/water-absorbing porous sheet.

(f) By selecting the combination of semipermeablemembrane/saccharide/water-absorbing sheet, a drip-absorbing sheet can beeasily prepared while using the saccharide as the adhesive.

As apparent from the foregoing description, the drip-absorbing sheet ofthe present invention has a simple structure and can be automaticallyprepared by using an appropriate apparatus without the need for a largelabor force. Moreover, the water-absorbing sheet of the presentinvention can be prepared by using materials admitted to be safe fromthe sanitary viewpoint, especially natural materials alone, themanufacturing cost can be reduced, and the reliability is high.

Moreover, since the water-absorbing sheet can be cut to a size suitablefor an intended use, no waste occurs. If appropriate materials areselected, when the used drip-absorbing sheet is discarded and burnt, aharmful gas is not generated, and when the drip-absorbing sheet isburied under the ground, the sheet is easily biologically decomposed andthere is no risk of environmental pollution. Accordingly, thedrip-absorbing sheet of the present invention is advantageous fromvarious viewpoints.

I claim:
 1. A drip-absorbing sheet comprising a powdery or granularedible saccharide supported and laminated between a semipermeablemembrane and a water-absorbing porous sheet, wherein the amount of thepowdery or granular edible saccharide is 10 to 200 g/m².
 2. Adrip-absorbing sheet as set forth in claim 1 wherein the weight of thewater-absorbing porous sheet is 0.2 to 10 times the weight of the ediblesaccharide.
 3. A drip-absorbing sheet as set forth in claims 1 or 2,wherein the semipermeable membrane and the water-absorbing porous sheetare partially bonded through an adhesive within a range not adverselyaffecting the water permeability
 4. A drip-absorbing sheet as set forthin claims 1 or 2, wherein an edible saccharide having a melting pointlower than the melting temperature or carbonization temperature of thesemipermeable membrane or water-absorbing porous sheet is used as thesaccharide, and the assembly is heat-pressed at a temperature lower thansaid melting temperature or carbonization temperature to melt thesaccharide and bond the semipermeable membrane and the water-absorbingporous sheet.